The present invention relates to an electronic leveling system, an electronic leveling apparatus and a leveling staff, and particularly to an electronic leveling system in which the electronic leveling unit can send various data generated on it to the leveling staff and the leveling staff can send various data generated on it to the leveling unit. The system is capable of calculating automatically the amount of modulation for the measurement result for compensating the tilt of the leveling unit and leveling staff through the detection of their tilt angles.
For the direct measurement of the ground level or the like, a set of leveling unit and leveling staff has been used conventionally. The leveler uses the leveling unit to view the scale on the leveling staff and measures the difference of height between positions. However, this traditional leveling scheme involves a read error made by the leveler. With the intention of overcoming the leveler's read error, electronic leveling systems in which the scale on the leveling staff is read electronically have been developed. One electronic leveling system is designed to emit a prescribed optical signal from the leveling staff and receive and identify the optical signal on the leveling unit thereby to read the scale on the leveling staff.
The applicant of the present invention has developed an electronic leveling apparatus that is operative to determine the height difference between positions electronically, as described in U.S. patent application Ser. No. 08/082,082. This electronic leveling apparatus uses a leveling staff 2 having a cyclic arrangement of a pattern set, with each block consisting of a first pattern A, second pattern B and third pattern R at a constant pitch of p, as shown in FIG. 2.
The lowest pattern block is defined to be block 0 which includes R(0), A(0) and B(0), the next block is block 1 including R(1), A(1), B(1), the next block is block 2 including R(2), A(2), B(2), and so on. A reference signal is produced in correspondence to the constant pattern pitch p. The third pattern R has a constant length of 8 mm for its black section, whereas the first pattern A has its length modulated to have a period of 600 mm and the second pattern B has its length modulated to have a period of 570 mm.
However, the above-mentioned electronic leveling apparatus for evaluating the height difference automatically cannot measure the height difference accurately if the leveling staff tilts or the ambient temperature varies.
In addition, it compels the leveler and workman to have a voiced communication, which often necessitates a transceiver set, for telling the readiness of the leveling staff or the like. The leveling staff having only the formation of scale pattern for electronic reading does not allow the leveler to have the visual measurement for the immediate verification of the result of electronic measurement.
Moreover, for the compensation against the tilt of leveling staff and the temperature variation, it requires a modifying calculation for the measured data based on the circumstantial data at each time of measurement. It requires a workman's hard work to set up a front and rear leveling staffs that need to be equidistant from the leveling unit at the determination of the starting point.